Devices for selecting and detecting at least two spectral regions of a light beam are known in the field and described, for example, in the form of a spectral detector in German Patent Application DE 101 02 033 A1. From DE 101 02 033 A1, in particular, it is known for a means for suppressing reflected and/or scattered light of an illuminating light of a microscope to be placed in the detection beam path before the detection device. In this connection, it is possible to suppress light of one excitation wavelength produced by a laser.
There are applications for which the suppression of reflected and/or scattered light using the known means is inadequate. Even when using, for example, a spectral detector and an AOBS, which together suppress excitation wavelengths by a factor of 10−6 (spectral detector 10−4 to 10−5 and AOBS 10−2), the amount of residual scattered light of the excitation wavelengths entering the spectral detector is often still so high that the dynamics, that is, the signal-to-noise ratio is thereby significantly reduced. An efficient bandpass filter already provides a suppression of 10−6. When combined with an efficient dichroic beam splitter with a residual transmission of the excitation wavelength of about 1%, the resulting total suppression is about 10−8. However, particularly for samples that are viewed close to the cover slip and which yield a low intensity of the excitation light and/or reflected light, residual light suppression using a spectral detector and an AOBS is not sufficient because both signals are of about the same order of magnitude.